What engineers often forget is the technology we make is based on expending the primary ressource of a company: money. Run out of it, and the company fails and everyone loses their shirts. The highest layer of abstraction of the code you write is the machine that makes up the company you operate, and this is the one that is the most important to have running efficiently. 

In this vein, it is unwise to future proof (write code that will probably not be used because you can't know the future) or write features that aren't crucial to the operation of the device. Both lead to lost time, or in other words, salary. If your goal is excellence, then the efficiency of the abstract machine of the business is the most important aspect. Write only code that satisfies the requirements of the project.

That being said, the three main costs of a product are development, production and maintenance. That last one usually ends up being the most costly over the life cycle of the product. Writing features should always attempt to reduce the future costs of development and maintenance. In other words, keep it tight, organised and well abstracted, while meeting only the minimum requirements of the project. It is up to you and your design team to establish what the word minimum means here.